1. Field of the Invention
The present invention relates to an aqueous ink (hereinafter may also referred to as “ink” merely) suitable for use in writing utensils such as aqueous ball point pens, fountain pens and aqueous marking pens, and particularly in ink jet printers, and to an ink jet recording method, an ink cartridge, and an ink jet recording apparatus.
2. Description of the Related Art
An ink jet recording system is a printing method in which minute droplets of an ink are ejected to apply the droplets to a recording medium such as paper, thereby conducting printing. According to this recording system, high-resolution and high-quality full-color images can be printed at a high speed by a cheap apparatus. However, the ink jet recording method has involved the following problems because the ink is liquid. More specifically, there has been a problem that when plain paper is used as a recording medium in particular, ink droplets permeate into the recording medium when the droplets have impacted on the recording medium, thereby causing an unclear contour part of an image. In addition, a phenomenon that boundary bleeding (i.e., color bleeding) occurs between adjoining different colors may have occurred in some cases.
On the other hand, in order to solve the above-described problems, a process in which a solution containing a polyvalent metal salt is applied to a recording medium and inks each containing a dye having at least one carboxyl group are then applied, has been proposed (see Japanese Patent Application Laid-Open No. H05-202328). In other words, according to this process, the solution containing a polyvalent metal ion (reaction liquid) comes into contact with the ink containing the dye capable of reacting with the ion on the recording medium, thereby forming insoluble matter. As a result, the unclearness at the contour part is improved, and the color bleeding is also prevented. In addition, a high-quality image with reduced strike-through of a coloring material to a back surface of the recording medium (hereinafter referred to as a strike-through characteristic) can be provided.
It has also been proposed to use a black ink having characteristics of thickening or aggregating by an action with a salt and a color ink containing the salt in combination. According to this proposal, a high-quality color image high in image density and free from occurrence of color bleeding is provided (see Japanese Patent Application Laid-Open No. H06-106735). In other words, according to this method, it is achieved to provide a good image by using, as a set, 2 liquids which reacts with each other when the liquids are mixed upon formation of the image (hereinafter referred to as a two liquid system). In addition, various proposals using 2 liquids have been made (see, for example, Japanese Patent Applications Laid-Open Nos. H03-240557 and H03-240558).